1. Field of the Invention
The present invention relates to light weight high strength particles and methods of treating subterranean producing zones with fluids containing the particles.
2. Description of the Prior Art
Treating fluids containing high strength particles are used in a variety of operations and treatments conducted in oil and gas wells. Such operations and treatments include, but are not limited to, well completion operations and production stimulation treatments.
An example of a well completion operation using a treating fluid containing particles is gravel packing. In gravel packing operations, particles referred to in the art as gravel are carried to a subterranean producing zone in which a gravel pack is to be placed by a hydrocarbon or water carrying fluid. That is, the particles are suspended in the carrier fluid which can be viscosified and the carrier fluid is pumped into the subterranean producing zone in which a gravel pack is to be placed. Once the particles are placed in the zone, the treating fluid leaks off into the subterranean zone and/or is returned to the surface. The gravel pack produced functions as a filter to separate formation solids from produced fluids while permitting the produced fluids to flow into and through the well bore.
An example of a production stimulation treatment utilizing a treating fluid having particles suspended therein is hydraulic fracturing. That is, a treating fluid, referred to in the art as a fracturing fluid, is pumped through a well bore into a subterranean zone to be stimulated at a rate and pressure such that fractures are formed and extended into the subterranean zone. At least a portion of the fracturing fluid carries particles, referred to in the art as proppant particles into the formed fractures. The particles are deposited in the fractures and the fracturing fluid leaks off into the subterranean zone and/or is returned to the surface. The particles function to prevent the formed fractures from closing whereby conductive channels are formed through which produced fluids can flow to the well bore.
As more oil and gas wells are being drilled in deep water into high temperature deep zones, gravel packing in long open horizontal well bores is becoming more prevalent. The completion of the wells requires light weight high strength particles that are high temperature and chemical resistant. In order to prevent damage to the producing zone in which a gravel pack is placed, the treating fluid carrying the particles is generally viscosified to a relatively low degree. As a result, the particles suspended in the treating fluid must be of light weight, i.e., the particles must have a specific gravity in the range of from about 0.7 to about 2.2.
The use of lightweight particles lowers the overall density of the fluid carrying the particles which directly reduces the hydrostatic pressure applied to the well bore and helps prevent unwanted fracturing of the well bore. In addition, the use of lightweight particles reduces the concentration of gelling agent required to viscosify the carrier fluid, thus minimizing the amount of gelling agent residue that remains within the packed bed of particles or which penetrates into the subterranean producing zone.
The same is true of fracture stimulation treatments carried out in deep, high temperature wells, i.e., light weight high strength spherical particles having specific gravities in the range of from about 0.7 to about 2.2 are required due to the use of lower viscosity fracturing fluids and the high temperature of the subterranean zones being fractured.
A variety of light weight particles formed of thermoplastic materials including polyolefins, polystyrene divinylbenzene, polyfluorocarbons, polyethers etherketones and polyamide imides are commercially available. However, when the thermoplastic particles are exposed to temperatures above about 150° F., the particles soften and deform. As a result, the thermoplastic polymers are generally limited to gravel packing wells having low temperatures and they are generally not applicable in hydraulic fracturing operations.
Thus, there are needs for improved light weight high strength particles for use in gravel packing and fracturing procedures that have high temperature and chemical resistance and have specific gravities in the range of from about 0.7 to about 2.2.